Road Vehicle Transport (RoRo: Road-vehicle on Road-vehicle)

Source: pulsexlb/OpenTTD-patches px-patch (September 2026 batch), merged into jrpm via git merge.

Overview

"Road vehicle transport" lets trains, ships and aircraft carry road vehicles directly:

• Road vehicles no longer have to drive everywhere on their own: they can "hitch a ride", being carried to a distant station and then driving off on the road network again;
• A carrier (train/ship/aircraft) gains the ability to carry road vehicles by being refitted to the "Vehicles (Road)" cargo (dedicated cargo label VEHC, which uses up cargo space);
• On the road-vehicle side, the order flags "Wait to be transported" and "Unload here" pair up with the carrier's "load road vehicles" / "unload road vehicles" order flags.

How to use

Carrier side (train/ship/aircraft)

1. Refit the train in a depot manually to the "Vehicles (Road)" cargo — refitting into a carrier can only be done manually; order-list refitting does not apply;
2. Enable "Load road vehicles" on a station order: the train picks up waiting road vehicles at that station;
3. Optional pairings:
   • "Wait for load" (depart only when loaded);
   • "Destination match": only load road vehicles whose declared unload station equals the carrier's next stop;
   • "Unload all road vehicles here": unload everything, ignoring each vehicle's declared station.

Road vehicle side

1. Set "Wait to be transported" on a station order: the vehicle stops there and waits for a carrier;
2. Set "Unload here": the vehicle drives off the carrier at this station;
3. The two options are mutually exclusive (one per order);
4. When unloaded, the road vehicle runs a pathfinder pass to pick the best platform to leave from.

Details and rules

• Dedicated cargo slot: road vehicle transport uses cargo slot 128 (NUM_CARGO - 1), outside the 64 slots NewGRFs can define; the total number of cargo types is extended from 64 to 128;
• Dedicated-carrier detection: when every part of a vehicle is refitted to "Vehicles (Road)", its order buttons default to road vehicle transport; vehicles carrying any normal cargo default to normal cargo;
• Carrier parts setting: vehicle.rv_transport_carrier_parts decides which parts may carry road vehicles (any part / oversized only / bulk+oversized+vehicles cargo);
• Cross-company loading: optionally allow loading/unloading other companies' vehicles with automatic fee settlement;
• "Carried too long" warning: a one-time warning when a road vehicle has been carried for too long;
• Player-created order lists: shared/standalone order lists support road vehicle transport flags as well.

Ships can additionally carry whole trains (dedicated RAIL cargo), added in the 2026-10 batch. See "Train Ferry and Rain".

Savegame compatibility

• Waiting/carried state and order flags are persisted;
• Old savegames (without the XSLFI_CARGO_TYPES_128 flag) are read with 64 cargo slots and stay compatible.

Console debug commands (off by default)

The rvtransport command family (list/wait/orderflag/attach/detach/selftest etc.) is only compiled with the CMake option RORO_DEBUG_COMMANDS=ON, for regression testing.

Related code

• Core: src/roadveh_transport.h, src/cargo_type.h (VEHC cargo)
• Orders: src/order_cmd.cpp, src/order_gui.cpp, src/order_base.h (OrderExtraInfo)
• Train loading: src/train_cmd.cpp, src/station_cmd.cpp
• Cargo extension: src/sl/station_sl.cpp, src/sl/company_sl.cpp (XSLFI_CARGO_TYPES_128)